This project seeks to purify and characterize the major classes of growth factors released by transformed human cells. This includes chemical and biological comparisons with known hormones like human somatomedins and animal cell growth factors such as Epidermal Growth Factor, Sarcoma Growth Factor, etc. A human fibrosarcoma cell line (8387) produces a growth factor related to multiplication stimulating activity (MSA) produced by a rat liver cell line grown in serum-free medium. MSA belongs to the insulin-like growth factor family of the somatomedins and interacts with the same receptors in various tissues. The 8387 growth factor and its specific binding protein were isolated. Comparisons were made with known human somatomedins and MSA-like growth factors from various tumor cell types. The purified binding protein was used to develop a human specific competitive binding protein assay to screen human tumor tissues for MSA-like material.